Night vision devices for motor vehicles are described, for example, in PCT Patent Publication No. WO 02/36389. They have night vision cameras, which, for example, on the basis of near infrared with active illumination (NIR) or on the basis of head radiation (FIR) take a picture of the surroundings of the vehicle with a visual range that normally exceeds the visual range of the human eye. The image of the surroundings of the vehicle is displayed to the driver via a display unit. The display unit may be a conventional display in a dashboard or a head-up display, which projects the image onto the windshield with the aid of a projector. Head-up projectors are described, for example, in German Patent Application No. DE 101 31 720.
Driving according to a display with the aid of the pure night vision image is relatively difficult since it is hard to estimate relative positions in the traffic lane by the displayed night vision image. Even on very well-constructed roads such as highways and superhighways, which have very good lane markings and large radii of curvature, driving according to a display of the night vision image is possible only with difficulty. In addition, the distance to other objects, particularly to preceding vehicles, is very hard to estimate. Even with great practice of driving according to a displayed night vision image, maintaining a suitable safety distance is possible only with difficulty since the night vision image was often shot using a different aperture angle than the picture perceived by the human eye through the windshield.
From German Patent Application No. DE 199 40 723, a method for displaying a perspective image is known, in which image elements are changed in at least one variable as a function of the travel path ahead, of at least one operating parameter of the vehicle and/or of at least one parameter of an object identified in the region of the travel path.